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<head>
    <meta charset="UTF-8">
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    <title>Document</title>
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<body>

    <script>
        function run(){
            var a = 10;

            // a++;
            // console.log(a) // 输出11

            // ++a;
            // console.log(a) // 输出11

            // var b = a++;
            // console.log(b)  // 输出10
            
            var b = ++a;
            console.log(b)  // 输出11
        }
        run();
    </script>
</body>
</html>